1. Field of the Invention
The present invention relates to organoalkoxysiloxanes, including mixtures of organoalkoxysiloxanes, to a process for manufacturing the organoalkoxysiloxanes and to the use of such mixtures.
2. Description of the Background
It is well-known to manufacture an organoalkylsilane by the esterification of an organochlorosilane with an alcohol.
It is also well-known to manufacture orthosilicic acid tetraalkylesters or their oligomers by esterification of tetrachlorosilane or oligomeric chlorosiloxanes, as described in DE 27 44 726 C2. In this process oligomerization can be performed by the addition of water in precise amounts simultaneously with esterification or in conjunction with esterification.
Because of the various hydrolysis or condensation characteristics of the monomeric educt and the resulting derivatives, control of the reaction for the production of oligomeric silicic acid esters is extremely difficult, in particular if the objective is to conduct esterification, hydrolysis and condensation simultaneously or continuously, particularly on the industrial scale. In addition, such systems should be as stable during storage as possible. That is, both physical and chemical properties such as oligomer distribution and viscosity should be maintained for as long as possible.
DE 28 09 871 C2 discloses a process for partial hydrolysis of orthosilicic acid tetra(alkoxyalkyl)ester, wherein the total quantity of water required for the desired extent of partial hydrolysis is already mixed in with the ester at the beginning of conversion.
EP 0 518 057 proposes a process for the production of organoalkoxysilanes by condensation or cocondensation of vinyl and/or alkylalkoxysilanes in the presence of a catalyst, wherein the calculated quantity of water is added in solution to the 0.2 to 8 times weight of methanol or ethanol.
EP 0 814 110 A1 (O.Z. 5063) also describes a process for the discontinuous production of C3 to C8-alkyltrialkoxysiloxanes by the condensation of corresponding alkylalkoxysilanes in the presence of hydrogen chloride (HCI), wherein more than 1 mol water per mol silicon is used for hydrolysis or condensation of the alkoxysilane.
EP 0 579 453 A2 proposes a process for manufacturing alkylalkoxysiloxanes, in particular, based on isobutyltrimethoxysilane (IBTMO), wherein 0.1 to 0.6 mol water per mol alkoxysilane is used for the objective hydrolysis. The result here is mixtures containing alcohols, in turn containing a high proportion of silane monomer, that is, educt, as a result of which the product exhibits a high proportion of volatile monomer when applied and which also has a low flash point.
A discontinuous method for the hydrolysis of isopropyltrimethoxysilane is also disclosed in J. Organometallic Chem. vol. 489 (1995).
U.S. Pat. No. 5,112,393 (WO 92/06101) discloses solvent-free organoalkoxysiloxanes having 2 to 9 Si units for the water-repellent coating of mineral building materials, wherein fluororganic compounds can be added to the siloxane in order to improve the repelling properties of the coating. U.S. Pat. No. 5,112,393 discloses C1 to C30-alkyl/cycloalkyl/arylalkyl/alkaryl or their mixtures as organo groups, and also olefinic organo groups and such groups substituted by heteroatoms or fluorine. Particular emphasis is given to siloxanes with C4 to C8-alkyl groups and an oligomerization degree of 2 to 4, wherein 1,3-di-n-octyl-1,1,3,3-tetramethoxydisiloxane and 1,3-di-n-octyl-1,1,3,3-tetraethoxydisiloxane are preferred. They, too, are manufactured discontinuously. In addition, the objective manufacture of these disiloxanes is expensive.
A method for the specific hydrolysis of alkoxysilanes is also known as disclosed in U.S. Pat. No. 5,543,173, wherein the product results in a substantial amount of alcohol by the hydrolysis reaction or considerable quantities of solvents such as toluene or methylisobutylketone (MIBK). U.S. Pat. No. 5,543,173 discloses, as educts, organoalkoxysilanes with organo groups such as aminoalkyl, diaminoalkyl, for example, N-2-aminoethyl-3-aminopropyl, vinyl, C6 to C20-alkyl, for example methyl, ethyl, i-propyl, n-butyl, in particular octyl, halogenoalkyl, methacryloxyalkyl or mercaptoalkyl. Here, too, alkoxysilanes which are prepared in a separate process by esterifying the respective chlorosilanes with an alcohol are used. Such discontinuous processes performed over several processing stages are as a rule expensive and cost-intensive.
It should also be emphasized that each of these organoalkoxysilanes, including the corresponding oligomeric siloxanes, has a different hydrolysis or condensation behavior which, accordingly, considerably complicates such processes being conducted on a production scale.
Accordingly, one object of the present invention is to provide a highly economical process for the continuous manufacturing of organoalkoxysiloxanes.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a process for the continuous manufacture of a mixture of mixture of organosiloxanes of formula I
[Rxe2x80x2O)zSi(R)(O)y]n[(Rxe2x80x2O)zSi(Rxe2x80x3)(O)yxe2x80x2]m 
wherein R and Rxe2x80x3 are identical or different and are methyl, ethyl, vinyl, n-propyl, i-propyl, xcex3-chloropropyl, n-butyl, n-pentyl, i-pentyl, n-hexyl, i-hexyl, n-heptyl, i-heptyl, n-octyl, i-octyl, hexadecyl, octadecyl or alkoxy, Rxe2x80x2 represents methyl or ethyl, n and m are identical or different and each is 0 or an integer ranging from 1 to 20, on the condition that (n+m)xe2x89xa72, y and yxe2x80x2 are  greater than 0 to 1.5 and z and zxe2x80x2 are 0 to  less than 3, wherein y and yxe2x80x2 and z and zxe2x80x2 are the same or different, and (2y+z)=3 and (2yxe2x80x2+z)=3, comprising:
reacting in a first stage (i) organotrichlorosilane or a mixture of organotrichlorosilanes, preferably alkyltrichlorosilanes, in particular n-propyltrichlorosilane and/or vinyltrichlorosilane or a mixture of at least one organotrichlorosilane and tetrachlorosilane, (ii) water, appropriately demineralized water and (iii) alcohol preferably methanol and/or ethanol in a molar ratio (i):(ii):(iii) of 1:(0.59 to 0.95):(0.5 to 100), preferably 1:(xe2x89xa70.6 to 0.9):(1 to 3), particularly preferably 1:(0.65 to 0.85):(1 temperature of 0 to 150xc2x0 C., preferably from 20 to 70xc2x0 C., particularly preferably at 40 to 60xc2x0 C., which produces hydrogen chloride as a gaseous product which is removed from the system and the crude organoalkoxysiloxane product is transferred proportionately to the reaction distillation column of a subsequent second stage by way of a preheater, if required, after an average dwell time of 0.5 to 180 minutes, preferably 1 to 60 minutes, particularly preferably 4 to 30 minutes in order to complete the reaction in the column, with the optional supply of an additional quantity of alcohol in a molar ratio of (i):(iii) of 1:(0.1 to 100), preferably 1:(0.5 to 10), particularly preferably 1:(1 to 3), is supplied; and
conducting reaction and distillation in the reaction distillation column in a second stage in which volatile constituents are withdrawn from the top of the column and the organoalkoxysiloxane product is withdrawn as a bottom product, wherein the reaction-distillation column is operated at a bottom temperature of 50 to 200xc2x0 C., preferably 100 to 180xc2x0 C., particularly preferably 150 to 170xc2x0 C.